Method and Apparatus for Manufacturing Asymmetrical Roll-Formed Sections

ABSTRACT

A roll-forming station for forming asymmetrical sheet metal beams with unequal flanges, where both of the unequal flanges contact the rolls simultaneously and where the diameters of the rolls are such that the bending moments applied to the unequal flanges are identical in magnitude. This prevents lateral displacement of the workpiece during forming.

FIELD OF THE INVENTION

The present invention relates to roll-forming, and more specifically toroll-forming asymmetrical sheet metal sections.

BACKGROUND

Roll-forming is a continuous bending operation in which a long flatstrip of sheet metal is passed through several sets of rolls mounted onroll stands, each set of rolls bending the strip incrementally furtherand further until the desired profile is obtained. Typically, theprocess is used for manufacturing constant-section beams.

While the e are many possible cross-sections that can be manufacturedthis way, when a cross-section is asymmetrical (such as anunequal-flange U-section), the rolls may not contact the workpiecesimultaneously, or the points of contact may not be equidistant from theaxial plane of the rolls. This results in lateral displacement of theworkpiece, which can cause twisting, bowing, and other defects, as theworkpiece passes through the subsequent roll stands.

A need therefore exists for a reliable method of centering anasymmetrical section as it passes through a roll stand, and of ensuringsimultaneous contact and equal torque on either side of an asymmetricalsection.

SUMMARY OF THE INVENTION

The object of the present invention is to develop a method for themanufacture of asymmetrical angles, channels, and other asymmetricalprofiles that includes additional technical steps for centering theworkpiece during bending by means of the simultaneous application ofopposite moments of the forming forces, and to develop a machine forimplementing this method, as well as to improve the structure of theroll stand and the rolls by changing their location and the interactionof the forming elements, as well as introducing a certain relationshipbetween their sizes.

While the below disclosure focuses on the method and machine formanufacturing an unequal-flange channel section, the invention is notlimited to the formation of such sections, but may also be used to formother asymmetrical section roll-formed sheetmetal sections, as a personof reasonable skill in the art shall find readily apparent. Nothing inthe below disclosure shall be understood to limit the invention to themanufacture of the roll-formed channel sections with unequal flanges.

One embodiment of the present invention comprises a roll stand intendedfor the manufacture of asymmetrical profile beams (with a longer flangeand a shorter flange) in which the dimensions of the rolls are such thatthe longer flange contacts its forming roll at the same time as theshorter flange contacts its forming roll, and the shape of the rolls aresuch that the bending moment applied to the longer flange by itscorresponding roll is nearly equal and opposite to the bending momentapplied to the shorter flange by its corresponding roll. Furthermore,the point of contact between the longer flange and its correspondingroll, and the point of contact between the shorter flange and itscorresponding roll, are equidistant from the central plane of the rolls.This prevents lateral displacement of the workpiece and the resultingtwisting and bowing defects in its manufacture. Due to the prevention oflateral displacement, it is possible to apply higher forces to theworkpiece, meaning that fewer roll stations are needed to achieve thedesired bending angles.

The rolls may be kinematically coupled or freely rotating. Also, one ormore of the rolls may be spring-loaded to ensure good contact with theworkpiece.

The present invention thus broadens the industrial possibilities for themanufacture of asymmetrical section roll-formed beams from coiled sheetmetal workpieces, due to the possibility of piecework manufacture andthe resulting simplification of the manufacturing process.

LIST OF FIGURES

FIG. 1 shows the moment at which the workpiece enters the rolls of anintermediate roll stand and the beginning of the simultaneous bending ofthe longer and shorter flanges of the channel section in accordance withthe present invention;

FIG. 2 shows a schematic illustration of a roll-forming machine forimplementing the claimed method;

FIG. 3 shows a schematic illustration of the coupled rolls in anintermediate roll stand, designed and installed in accordance with thepresent invention;

FIG. 4 shows a schematic illustration of the coupled rolls in a rollstand with the vertical roll driven by the horizontal roll by means oflinked conical gears;

FIG. 5 shows a schematic illustration of a non-driven disc-shapedforming element on the driven roll for bending the shorter flange of thechannel section.

On the drawings are shown:

FIG. 1: 1—the longer flange of the channel section; 2—the shorter flangeof the channel section; 3—the workpiece at the moment it enters therolls of an intermediate roll stand and the roll-formed section beginsto be formed; 4—the central region of the section; 5—the calibrationplane (axial plane of the rolls); 6—the female side roll of the rollstand for bending the longer flange of the section; 7—the vertical axisof rotation of the roll for bending the longer flange of the section;8—the female lower roll for bending the shorter flange of the section;9—the horizontal axis of rotation for the roll for bending the shorterflange of the section; 10—the spacing between the rolls; 11—the maleupper roll with a horizontal axis of rotation.

FIG. 2: 12—uncoiler for the coiled sheetmetal workpiece;13—straightening machine; 14—shears; 15—welding machine; 16—the feedrolls; 17—workpiece holder; 18—straightening machine; 19—flying cutter;20—roll-forming machine; 21—intermediate roll stand; 22—roller conveyor.

FIG. 3: 23—forming (and calibrating) region of the roll 6 for bendingthe longer flange of the section; 24—calibrating section of the roll 8for bending the shorter flange; 25—directing surface for entry of theshorter flange of the roll-formed section into the working groove of theroll for bending; 26—working shaft of the female roll with a horizontalaxis of rotation; 27—cylindrical forming element of the roll;28—disc-shaped forming element with a conical calibrating region;29—spacer; 30—nut; 31—disc element of the frictional transmission.

FIG. 4: 32—conical gear of the vertical roll; 33—conical gear of thehorizontal roll; 34—roll spacer.

FIG. 5: 35—disc-shaped freely rotating forming element; 36—bearing formounting the disc-shaped freely rotating forming element on the shaft;37—spacer for mounting the bearing on the shaft; 38—spacer for mountingthe bearing on the shaft.

K—the point of contact between the longer flange of the roll-formedsection and the vertical roll; *K—the location of point K on theroll-formed section in the rolls; M—the point of contact between theshorter flange of the roll-formed section and the horizontal roll;*M—the location of point M on the roll-formed section in the rolls;Z_(k)—the distance between point K and the center plane of the rolls, m;Z_(M)—the distance between point M and the center plane of the rolls;D_(d.k) and D_(d.f)—main diameters of, respectively, the vertical femaleroll used for bending the longer flange of the channel section and thehorizontal female roll used for bending the shorter flange of thechannel section; D_(d.m)—main diameter of the male rolls; (D_(d.k),D_(d.f), and D_(d.m)—the diameters, respectively, of the vertical femaleroll, the horizontal female roll, and the horizontal male roll); b_(s)and b_(b)—respectively, the width of the shorter and longer flange ofthe section; h_(s) and h_(b)—respectively, the height of the sectionmeasured from the shorter and longer flange of the section; α andΔα—respectively, the total bending angle of the longer flange of theroll-formed section in the preceding roll stands and the bending anglein the current roll stands; β and Δβ—respectively, the total bendingangle of the shorter flange of the roll-formed section in the precedingroll stands and the bending angle in the current roll stands;δ—difference between the cross-sectional radius (d_(M)/2) of thehorizontal female roll and its nominal radius at the entry point of theshorter flange of the working groove of the roll at point M (where theedge of the profile contacts the roll); T—the region of contact betweenthe two female rolls; P—force applied to create frictional forcesbetween the side roll and the bottom driven roll, H; D_(T.h) andD_(T.K)—the diameters of the ring-shaped contact regions including pointT on the horizontal and vertical rolls, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A method of manufacturing an unequal-flange channel section profile isdescribed below as the preferred embodiment. It is to be understood thatthe invention is not limited to that particular profile, but isapplicable to any other asymmetrical profile. FIG. 1 shows anintermediate stage in roll-forming an unequal-flange channel sectionprofile 3. The longer flange 1 and the shorter flange 2 are bent inrelation to the central region 4. The contact between the longer flange1 and its forming roll is simultaneous with the contact between theshorter flange 2 and its forming roll. Also, the point of initialcontact between the longer flange 1 and its forming roll is equidistantfrom plane 5 to the point of initial contact between the shorter flange2 and its forming roll. The roll used to bend the longer flange 1 is thevertical female roll 6 (its vertical axis of rotation is 7), and theroll used to bend the shorter flange 2 is the horizontal female roll 8(its horizontal axis of rotation is 9). Thus, the rolls used to form theunequal-flange channel section are the two female rolls 6 and 7 and thehorizontal male roll 11.

As an example of this embodiment of the present invention, suppose anintermediate roll stand is bending the flanges of the roll-formedsection that are 70 mm and 25 mm in width, with a 50 mm central wall.The bending angles for the longer flange of the roll-formed section areα=60° and Δα=15°; those for the shorter flange are β=60° and Δβ=15°. Theanalysis that has been performed on the initial stage of forming theprofile with the above parameters has shown that the simultaneouscontact between both flanges of the roll-formed section and thecorresponding rolls happens at equidistant points K and M from thecross-sectional plane of the rolls in the roll stand, i.e. whenZ_(k)=Z_(M). If distance Z_(k) exceeds distance Z_(M), the longer flange1 will contact roll 6 before the shorter flange 2 contacts roll 8. Thiswill result in lateral displacement, bowing, and twisting of the sectionin the direction of the longer flange. If distance Z_(k) is smaller thandistance Z_(M), the shorter flange 2 will contact roll 8 before of thelonger flange 1 contacts the vertical roll 6. This will result inlateral displacement, bowing, and twisting of the section in thedirection of the shorter flange.

The simultaneous contact between the unequal flanges of the roll-formedsection with the forming rolls at points K and M and their simultaneousbending relative to the central region 4 of the profile in at least oneroll stand is what prevents lateral displacement of the part from thecentral axis of the profile and thus improves the reliability of itsmanufacture. The application of forming forces by the rolls to thesection at the places of their initial contact with both flanges of theroll-formed section at the same distance from the cross-sectional plane,with the vertical female roll used to bend the longer flange of thechannel section and the horizontal female roll used to bend the shorterflange of the section, avoids bowing and twisting of the roll-formedsection in the rolls. This broadens the technical applications of thismethod, simplifies and speeds up the forming process, and enablesgreater bending angles to be used. Furthermore, this increases the rangeof manufacturable asymmetrical channel sections (which are difficult tomanufacture) and prevents manufacturing defects.

FIG. 2 shows a roll-forming machine to implement the preferredembodiment of the present invention. It comprises an uncoiler 12 for therolled sheet metal of the workpieces, a straightening machine 13 thatstraightens the workpiece, a guillotine cutter 14 to cut the ends of theworkpiece, a spot welding machine 15 to weld the front end of the coiledworkpiece with the end of the prior roll, and feeder rollers 16 to feedthe workpiece into the accumulator 17 that accumulates a sufficientlength of workpiece to coordinate the workings of the different machinesand mechanisms with different speeds, and to enable the continuousoperation of the machine. The machine also comprises a secondstraightening machine 18, a flying cutter 19 for cutting the workpiecesto the desired length, and the roll-forming machine 20 containing rollstands 21, including roll stands comprising coupled forming rolls withvertical and horizontal axes of rotation. A roller conveyor 22 is usedto transport the finished roll-formed sections to the packer. FIG. 3shows one of the roll stands (roll stand 21) of the roll-forming machineof the preferred embodiment of the present invention. The firstcalibrating region 23 of the longer flange 1 is placed in the verticalfemale roll 6 with axis of rotation 7, and the second calibrating region24 of the shorter flange 2 is placed in the horizontal female roll 8with axis of rotation 9. The working surface of the first calibratingregion 24 is adjacent to a tangent surface 25, and the magnitude of thediameter D_(d.k) of the vertical female roll 6 is determined by themagnitude of the diameter D_(d.f) of the horizontal female roll 8 andthe other dimensions of the profile as described in the followingformula (1):

D _(d.k) =[D _(d.f) +b _(s) cos β tan(β+Δβ)+δ+b _(s) sin β] [b _(s) cosβ tan(β+Δβ)+δ−b _(s) sin β]×[cos α−sin α/tan (α+Δα)]⁻¹ b _(b) ⁻¹ +b_(b)[cos α+sin α/tan(α+Δα)],  (1)

where D_(d.k) and D_(d.f) are the main diameters of, respectively, thevertical female roll 6 and the horizontal female roll 8;

b_(s) and b_(b) are, respectively, the design widths of the shorter andlonger flanges of the section: b_(s)=(b_(s))_(r)+R_(s)tan α/2,b_(b)=(b_(b))_(r)+R_(b)tan β/2;

(b_(s))_(r) and (b_(b)), are, respectively, the widths of the flatregion of the shorter and longer flanges of the section;

R_(s) and R_(b) are, respectively, the external radii of the transitionregion from the shorter and longer flanges of the roll-formed section tothe central region of the section;

α and Δα are, respectively, the total bending angle of the longer flangeof the roll-formed section in the prior roll stands and the bendingangle in the given roll stand;

β and Δβ are, respectively, the total bending angle of the shorterflange of the roll-formed section in the prior roll stands and thebending angle in the given roll stand;

δ is the difference between the actual value of the radius of thecross-section of the horizontal roll and its nominal value at the entryof the shorter flange of the roll-formed section into the working grooveof the roll, specifically at the point that the edge of the workpiecefirst meets the roll.

The analysis of the early stages of the forming process has shown thatin accordance with formula (1), the simultaneous contact between the twoflanges of the roll-formed section with the rolls occurs at points K andM that are equidistant from the cross-sectional plane, i.e. whenZ_(k)=Z_(M). Also, the direction of motion of the roll-formed sectionthrough the rolls must be along a straight line, and the wall 4 of theprofile must be located at the level of forming. If the distance Z_(k)is greater than distance Z_(M), then when the roll-formed section entersthe rolls, the longer flange 1 contacts vertical female roll 6 beforethe shorter flange 2 contacts horizontal female roll 8. This results inlateral displacement, bowing, and twisting of the section in thedirection of the longer flange of the section. If the distance Z_(k) isless than distance Z_(M), then when the roll-formed section enters therolls, the shorter flange 2 contacts horizontal female roll 8 before thelonger flange 1 contacts vertical female roll 6. This results in lateraldisplacement, bowing, and twisting of the roll-formed section in thedirection of the shorter flange of the section.

The rolls of the roll stand should preferably be composite. For example,the composite horizontal female roll 8 contains shaft 26 that supportsthe disc-shaped forming elements 27 and 28, spacer 29, and nut 30 (thebushing is not shown). This type of roll is simpler to manufacture andto use.

Shaft 26 can also support a disc frictional element 31 or a conical gearfor rotating the side vertical roll. The frictional transmission may beaccomplished by spring-loading one of the rolls with a spring force P atthe point of contact (point T in FIG. 3). The diameters D_(T.h) andD_(T.K) of the ring-shaped regions of contact that contain point T,respectively on the horizontal and vertical rolls, determine therotation speed of the significant points of the working surface of thevertical roll.

FIG. 4 shows a roll stand of the machine, in which the vertical femaleroll 6 is kinematically linked with the driven horizontal shaft 26 by,for example, conical gears. The conical gears 32 and 33 are rigidlymounted to the vertical female roll 6 and the shaft 26, respectively,along with a spacer 34, the disc-shaped forming elements 27, 28, and 29,by means of a bushing and a nut 30. The recommended kinematic linkagebetween the rolls during forming prevents a difference in velocitybetween the section and the rolls at the points of contact, and thusprevents dents and edge crumpling of the longer flange of the channelsection during forming as well as its lateral displacement and theresulting bowing and twisting.

In order to improve the quality of the sections and to reduce frictionallosses during bending, the forming element of the roll used for bendingthe shorter flange of the roll-formed section may be designed to freelyrotate on the shaft of the horizontal roll, for example on a bearing.FIG. 5 shows this configuration of a non-driven forming disc-shapedelement 35 for bending the shorter flange of the channel section onbearing 36 on shaft 26.

The incline angle of the forming surface of the forming region of thevertical female roll 6 and the horizontal female roll 8 are identicaland correspond to the bending angles of the shorter and longer flangesof the channel section. The main diameter of the vertical female roll 6is determined by formula (2):

D _(o.k) =[D _(o.h) +b _(s) cos α tan(α+Δα)+δ+b _(s) sin α] [b _(s) cosα tan(α+Δα)+δ−b _(s) sin α]×[cos α−sin α/tan(α+Δα)]−¹ b _(b) ⁻¹ +b_(b)[cos α+sin α/tan(α+Δα)],   (2)

where α and Δα, respectively, are the total bending angle of one of theflanges of the channel section in the prior roll stands and the bendingangle in the given roll stand. Due to the shape of the rolls, the twoflanges of the channel section contact the forming rolls simultaneously.

It must be noted that when the two flanges of the roll-formed sectionare bent at 90°, the working surface of the vertical female roll 6 isthe cylindrical surface, while the working surface of the horizontalfemale roll 8 is the flat surface of the disc-shaped element.

1. A roll stand, comprising: a first roll for forming a first flange ofa sheetmetal beam; a second roll for forming a second flange of asheetmetal beam, said second flange a different length from the firstflange; such that when the sheetmetal beam enters the roll stand, thefirst flange contacts the first roll at the same time as the second rollcontacts the second flange.
 2. The roll stand of claim 1, where thebending moment applied to the sheetmetal beam by the first roll isnearly identical in magnitude to the bending moment applied to thesheetmetal beam by the second roll.
 3. The roll stand of claim 1, wherethe point of contact between the first flange and the first roll and thepoint of contact between the second flange and the second roll areequidistant from the cross-sectional plane of the rolls.
 4. The rollstand of claim 1, where the sheetmetal beam is an asymmetrical channelsection beam.
 5. The roll stand of claim 1, where the first roll iskinematically linked to the second roll.
 6. The roll stand of claim 1,where at least one of the rolls rotates freely.
 7. The roll stand ofclaim 1, where at least one of the rolls is spring-loaded.
 8. A methodof manufacturing a sheetmetal beam comprising a first flange and asecond flange, the first flange not equal in length to the secondflange, comprising at least one roll-forming step where the first flangecontacts a roll at the same time as the second flange contacts a roll,and where the bending moment applied to the first flange is identical inmagnitude to the bending moment applied to the second flange.